A defendant in the Oakland carjacking of former state Senate President Pro Tem Don Perata has been sentenced to more than 18 years in prison, a prosecutor said Wednesday.

Ryan McGough, 29, was one of two men who carjacked Perata on Dec. 29, 2007. Ten days later, the other carjacker, Jared Adams, robbed a gas station during which he fired shots. One of the bullets paralyzed a 10-year-old boy as he practiced the piano at a music school across the street.

Although McGough was not involved in the incident that paralyzed Christopher Rodriguez, he and Adams' girlfriend, Maeve Clifford, took part in a two-week crime spree that was motivated by a desire to steal fancy tire rims and other designer car parts, prosecutors said.

At a hearing Monday in Alameda County Superior Court in Oakland, Judge Larry Goodman sentenced McGough to 18 years and three months in prison for robbery with use of a gun, carjacking, auto theft and being a felon in possession of a gun.

Adams, 26, was sentenced in June to 70 years to life in prison at an emotional hearing at which Christopher, who uses a wheelchair, shook Adams' hand and told him, "I forgive you."

McGough had agreed to testify against Adams at his trial. But when he was interviewed by Nancy O'Malley, chief assistant district attorney, "he was not honest about what had happened," the prosecutor said.

As a result, "I made the decision that I would not put him on the stand because I did not trust he would tell the truth," O'Malley said.

The prosecutor said she believed Adams was "the leader of this criminal enterprise" and that McGough was a follower.

Clifford, 20, is expected to be sentenced to six years in prison on Sept. 24.